In order to provide coverage over a particular area, mobile communications networks tend to be organised on a cellular basis, each cell representing an area within which a mobile terminal device may communicate wirelessly with a corresponding cellular base station, each cellular base station being interlinked by a communications network. A mobile terminal device moving from one cell, where it was communicating via a first base station, to another cell corresponding to a second base station must undergo “handover” between the first base station and the second in order for the communication to continue once it moves out of range of the first base station. Each base station operates at a different frequency and hence the handover involves a change of communication frequency. The process of handover can cause slight interruptions to communication which, in the case of voice or other mobile telephony applications, is not a critical factor. However, if applied to higher data rate communications, for example to the streaming of live differentially-coded video, even slight interruptions in communication of a few microseconds can result in irrecoverable data loss and image degradation for some period of time beyond the interruption.